Exam 1.4: Principles of Radiography and Definitions

Question 1

Physical properties of x-rays

Answer 1

Weightless and undetectable by human senses

Question 2

What is notable about how x-rays travel?

Answer 2

Travel in straight lines

Cannot be focused on a convergent point

Question 3

What allows x-rays to penetrate our tissues?

Answer 3

Short wavelength

Question 4

What is the difference between diagnostic and therapeutic radiation?

Answer 4

Therapeutic radiation causes a biological change

Question 5

What is the tube made up inside the tube head?

Answer 5

Pyrex glass

Question 6

What is inside the pyrex glass tube

Answer 6

Two electrodes

Also, no air….vacuum tube

Question 7

What is the negative electrode called

Answer 7

Cathode

Question 8

What is the function of the cathode?

Answer 8

It is the source of electrons

Question 9

What is the cathode made of

Answer 9

Tungsten filament wound up inside a Molybdenum cup

Question 10

Is the cathode stronger when it is thick or thin?

Answer 10

Thin

Question 11

How does the cathode “release” electrons

Answer 11

The cathode has a very high melting point, when heated the electrons boil off

Question 12

What is the name of the positive electrode?

Answer 12

Anode

Question 13

What is the function of the anode

Answer 13

It is the target of the electrons released by cathode. It releases the radiation

Question 14

What is the anode made from

Answer 14

copper with a tungsten target

Question 15

What percent of the energy produced by the anode is immediately lost as heat?

Answer 15

99%

Question 16

What happens to the x-ray’s energy when it scatters?

Answer 16

It is lowered

Question 17

What does scatter cause in terms of image errors?

Answer 17

Fog

Question 18

What is dangerous about scatter?

Answer 18

It is a source of patient exposure

Question 19

What does it mean when the x-ray is attenuated?

Answer 19

It has been absorbed by the tissue

Question 20

What values are important when trying to determine if an x-ray will be attenuated?

Answer 20

Wavelength
Tissue thickness
Atomic number
Density

Question 21

What is removed from the beam as it passes through, and is attenuated by tissue?

Answer 21

Photons

Question 22

What is the result of attenuation on the image?

Answer 22

Radiopacity

Question 23

What are the two most attenuating tissues in the body?

Answer 23

Enamel and Cortical Bone

Question 24

What results in complete attenuation of x-rays?

Answer 24

Metal restorations

Question 25

In a BW, what percent of x-rays pass through the tissue completely (transmitted) without any interaction at all?

Answer 25

9%

Question 26

If you want to increase the amount of x-rays in the beam (Cross sectional Density/Flux) what adjustment would you make to the machine?

Answer 26

Increase mA

Question 27

What value dictates the penetrating power of the beam?

Answer 27

kVp

Question 28

What is the primary safety feature of well designed x-ray systems?

Answer 28

Dead man switch

Question 29

What is the inverse square law?

Answer 29

Intensity (I) = 1/d^2

Question 30

What is the general idea of the inverse square law?

Answer 30

Intensity of radiation varies inversely with the square of the Source-Film Distance

Question 31

If you increase the Source to Film distance by 2x...what is the effect on the intensity of the beam?

Answer 31

The intensity of the beam is decreased by a factor of 4

Question 32

What is the purpose of the thin lead sheet in the film?

Answer 32

Receives radiation and protects patient from scatter

Question 33

Should the raised dot face the tube or the patient?

Answer 33

tube

Question 34

What are the three types of film?

Answer 34

Periapical (#1,2) Bitewing (#2) Occlusal (#4)

Question 35

What is determined by the film speed?

Answer 35

The efficiency with which a film responds to x-ray exposure

Question 36

If you increase the speed of the film, how would you adjust exposure time?

Answer 36

You would decrease it

Question 37

Which speed (High or Low) requires less radiation exposure for the patient?

Answer 37

Fast

Question 38

Film speed ratings are designated by the letters of the alphabet from A-F....is F the fastest or the slowest film?

Answer 38

F for Fast

Question 39

What does the sharpness of an image refer to?

Answer 39

AKA Definition, sharp images have a clear demarcation between all elements of the film

Question 40

What are some qualities that make an image "diagnostic quality"?

Answer 40

Exactness of anatomic detail | Proper balance of visibility and sharpness of redorded detail

Question 41

What is radiographic density?

Answer 41

White areas vs Dark areas on film

Question 42

What is the controlling factor of image density?

Answer 42

mAs | milliamperage seconds

Question 43

If you increase the mAs of the machine, what is the result (in terms of the beam)

Answer 43

The beam will now include more photons

Question 44

If you are going to increase mAs, try to do it by this amount

Answer 44

2x

Question 45

What is the controlling factor of contrast?

Answer 45

kVp

Question 46

What is the kilovoltage of the beam

Answer 46

The strength (not volume/amount) of x-rays. Increased strength means increased penetration of tissue

Question 47

What characteristic describes the diffusion of detail in an image?

Answer 47

Geometric unsharpness

Question 48

What would you call a fuzzy, unsharp margin around a structure on a radiograph

Answer 48

Penumbra

Question 49

What exactly is meant by image magnification?

Answer 49

EQUAL enlargement of all parts of the image. The shape of the magnified image is in the same proportion as the original

Question 50

How does image shape distortion differ from magnification

Answer 50

It is enlargement without keeping the enlarged image in the same proportion as the original

Question 51

If the x-rays are traveling from their source in diverging straight lines, what type of image distortion will occur?

Answer 51

Magnification

Question 52

If the x-rays originate from an area rather than a point what type of distortion will occur?

Answer 52

Geometric Unsharpness

Question 53

Why might different parts of the tooth be magnified to different extents

Answer 53

Because the teeth have depth, meaning the buccal cusps will show more magnification than the lingual cusps because they are further away from the film

Question 54

What are some keys to getting an acute image?

Answer 54

``` Small focal spot Longest source to film distance Shortest object to film distance Long axis parallel to film Central Ray perpendicular to film ```

Question 55

What will increasing the source to object distance and minimizing the film to object distance help mitigate?

Answer 55

Penumbra and Magnification

Question 56

What will keeping the film parallel to the long axis and the central ray perpendicular to the film help mitigate?

Answer 56

Geometric Distortion